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    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>

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<script>
    function Father(uname, age) {
        //this 指向父构造函数的对象实例
        this.uname = uname;
        this.age = age
    }
    function Son(uname, age, score) {
        //this 指向子构造函数的对象实例
        Father.call(this, uname, age) //把father中的this指向子构造函数中的this
        this.score = score
    }
    var son = new Son('小红', 66, 55)
    console.log(son);
</script>

</html>